The present invention relates to a method and apparatus for conveying a belt-shaped metal material, particularly a metal web, stably at a predetermined position in a liquid medium.
In the electrolytic treatment of the surface of a metal material of aluminum or iron, various treatments such as plating, electrolytic polishing, electrolytic etching, anodic oxidizing, electrolytic coloring and scraping treatments are extensively employed. In addition, a continuous electrolytic treatment method in which such an electrolytic treatment is continuously applied to a metal web is also known in the art.
FIG. 1 is a schematic sectional view showing the arrangement of an example of an apparatus which operates in accordance with a conventional continuous electrolytic treatment method. In FIG. 1, a metal web 1 supplied from a metal web roll is conveyed into an electrolytic bath 31 by rolls 21 and 22 and out of the electrolytic solution 30 in the electrolytic bath by rolls 23 and 24. An electrode 40 is arranged in the electrolytic bath 31 confronting the metal web running between the rolls 22 and 23. A voltage is applied between the electrode 40 and current supplying rolls 25 and 26 so that current flows between the metal web 1 and the electrode 40 through the electrolytic solution 30 to subject the metal web 1 to electrolytic treatment.
In order to provide a uniform electrolytic treatment on a metal web using such a continuous electrolytic treatment method, it is essential that the surface of the electrode which confronts the metal web be maintained parallel to the surface of the metal web which is subjected to the electrolytic treatment. In order to satisfy this requirement, a technique has been employed in which the electrode surface is made flat and the metal web is run with tension imposed on the metal web between the rolls 22 and 23 whereby the metal web surface is maintained parallel to the electrode surface.
As shown in FIG. 1, the electrolytic solution in a tank 34 is supplied into the electrolytic bath 31 through an electrolytic solution supplying inlet 32 by a pump P while the electrolytic solution 30 is returned to the tank 34 through an electrolytic solution discharging outlet 33. That is, the electrolytic solution is circulated by the pump P in such a manner as to maintain factors such as the composition, concentration and temperature of the electrolytic solution 30 unchanged. Due to the recirculation, the flow of the electrolytic solution through the electrolytic bath 31 tends to be irregular or turbulent. The turbulent flow affects the metal web running between the rolls 22 and 23 causing it to vibrate or shake. Thus, in practice, it is difficult to maintain the metal web parallel to the electrode surface. Furthermore, the above-described method is ineffective in maintaining the metal web parallel to the electrode surface in the widthwise direction of the metal web. Accordingly, the distance between the side portions of the metal web and the electrode surface is often different from the distance between the central portion of the metal web and the electrode surface. In general, the side portions of the metal web tend to drape downward compared to the central portion. Thus, frequently the side portions of the metal web have a different electrolytic treatment surface finish than the central portion.
Accordingly, an object of the invention is to provide an improved web conveying method and apparatus with which a metal web is run at predetermined positions, for instance, in a continuous electrolytic treatment bath.
A more specific object of the invention is to provide a method and apparatus for conveying a metal web through an electrolytic solution in an electrolytic treatment bath in such a manner that the metal web surface is maintained strictly parallel to an electrode surface.
Another object of the invention is to provide a method and apparatus for conveying a metal web through an electrolytic treatment bath in which the metal web is run without being affected by turbulent flow of the electrolytic solution in the region where the metal web confronts the electrode surface thereby to subject the metal web to uniform electrolytic treatment.
A further object of the invention is to provide a metal web conveying method and apparatus in which a metal web surface is maintained parallel to an electrode surface even in the widthwise direction of the metal web in an electrolytic treatment bath whereby the metal web is subjected to uniform electrolytic treatment even in the widthwise direction of the metal web.
A still further object of the invention is to provide a web conveying method and apparatus which is applicable to the conveyance of a variety of webs in which a predetermined part of the web in a liquid medium is maintained planar with a high precision.